Prior Art
A Stuart et al U.S. Pat. No. 3,470,057 discloses a pipe wrapping machine having a generally U-shaped frame for wrapping a pipe with a hot-applied tape. The apparatus disclosed in the Stuart et al patent includes an arm-lock assembly having wheels to retain the machine on the pipe in a rotatable manner. Pressure is applied against the pipe by the wheels of the arm-lock assembly to hold the machine against the pipe by adjustably disposing two sets of wheels in appropriate slots in the frame member and by spring biasing a third set of wheels inwardly toward the pipe across a mouth of the frame to resiliently secure the conduit between the three sets of wheels. Difficulties have been encountered in achieving consistent tape wrapping under constant tension with the apparatus shown in the Stuart patent. It has been found by applicant that one of the problems with the Stuart et al apparatus results from the resiliently attached third set of wheels not maintaining a constant pressure against the pipe during rotation of the apparatus. Because of the weight of the Stuart et al apparatus, the spring biasing force against the pipe is substantially changed as the apparatus is helically rotated around the pipe, particularly when the spring biased wheels are disposed on the top surface of the pipe, causing inconsistently applied pressure against the pipe from the various apparatus supporting wheels, at various rotational dispositions of the apparatus on the pipe. The tape, therefore, is not consistently applied under precise tension around the outer surface of the pipe and may cause inconsistent tape adherence.
Further, the Stuart et al apparatus suffers from various inconsistencies in angular alignment of the tension applying wheels and has no apparent provision for precisely fixing the angular disposition of the apparatus support wheels or the tape feeding assembly for fixing a desired degree of tape overlap without tape distortion, such as stretching.